4 WEALDEN AND PURBECK FOSSIL FISHES. 



three fused together. One or two large hook-shaped dermal spines, each on a 

 triradiate base, immediately behind the orbit, at least in males. 



Type Species. — The generic name Hyhodus appears to have been given by 

 Agassiz first to some teeth from the German Muschelkalk known as Ihjhoduii 

 j)licatilis (quoted, without description, by F. A. v. Alberti, Jahrb. f. Min., Geogn., 

 etc., 1832, p. 227). It was not defined until he had examined specimens from the 

 Lower Lias of Lyme Regis, Dorsetshire, showing the teeth and dorsal fin-spines in 

 natural association (L. Agassiz, Poiss. Foss., vol. iii, pp. 41, 178). Hyhodus 

 reticulatus, from that formation and locality, was the first species satisfactorily 

 described, and may therefore be regarded as the type (L. Agassiz, t.oni. cit., p. 180, . 

 pi. xxiv, fig. 26; pi. xxiia, figs. 22, 23). 



Remark^.- — The known specimens of the several species of Hyhodus from the 

 Lower Lias of Lyme Regis exhibit not only the arrangement of the dentition and 



Fig. I.—Hyhoihis hnvffianus, Fraas ; fish in left side view, with traces (.t sutt parts, iiicludinfj tlie fins, 

 about one-fifteenth nat. size. — Upper Lias ; Holzmaden, Wiirtemberg. University Geological 

 Museum, Tubingen. 



the dermal armature, but also the cartilages of the jaws, the neural and hfemal 

 arches of the trunk bounding a vacant space for the notochord, and the cartilages 

 of the pectoral arch. Specimens of another species from the Upper Lias of 

 Wiirtemberg are still more satisfactory, and one example prepared by Mr. Bernhard 

 Hauff shows distinct remains even of the fins (Text-fig. 1).^ A specimen from the 

 Lithographic Stone (Lower Kimmeridgian) of Bavaria displays the five branchial 

 arches and the cartilages of the pectoral fin.- A more imperfect specimen from 

 the same formation in the Montsech, Lerida, Spain, shows the neural arches, 

 slender ribs, and the cartilaginous support of the anterior dorsal fin.'' Another 

 fragment from the L^pper Beaufort Beds of Orange River Colony, South Africa, 

 exhibits the supports of a dorsal fin.^ The well-preserved skulls and portions of 



^ Hybochts hanffianus, E. Fraas, E. Kokeu, Geol. u. Palseout. AbLaiidl., n. s., vol. v (1907), pp. 

 261 — 276, pis. xi — xiii. 



- Hyhodus fraasi, C. Brown, Palaeontographica, vol. xlvi (1900), pp. 151—158, pi. xv. 



^ Hyhodus woodwardi, L. M. Vidal, Bol. lust. Geol. Espana, 1915, p. 22, pi. ii, text-figs. 4 — 6. 



* Hyhodus africanus, R. Broom, Ann. S. African Museum, vol. vii (1909), p. 252, pi. xii, fig. 2. 



